Method for the production of a plastic product having a hard plastic component and a soft plastic component, and plastic product produced using said method

ABSTRACT

A plastic product having a hard plastic component and a soft plastic component that adheres to the hard plastic component via at least one boundary surface is produced as follows: initially the soft component is injection molded in an injection molding die. Then the hard component is injection molded. In the plastic product produced in this manner, the soft component is surrounded over at least part of the circumference thereof by the hard component in the circumferential direction about a main demolding direction of the injection molding die. The result is a plastic product, wherein the shape and arrangement of the soft component can be tailored to functional requirements more flexibly.

The invention relates to a method for the production of a plasticproduct having a hard plastic component and a soft plastic component.The invention furthermore relates to a plastic product produced usingsuch a method.

Two-component plastic products of this type are known in many differentembodiments from the prior art. The soft component often serves as asealing element, or for improving the tactile qualities of a hardcomponent main body of the plastic product, for example as a handleelement, such as in a toothbrush. Furthermore, plastic products areknown in which a hard component is subsequently joined to a softfunctional component for sealing, connecting, damping, or improving thetactile qualities. Such a subsequent joining, as a rule, adds time andexpense.

It is therefore an object of the present invention to improve a plasticproduct of the type mentioned at the outset, in such a way that the softcomponent can be more flexibly tailored in its shape and arrangement tofunctional requirements.

This object is achieved according to the invention with a productionmethod for the plastic product having the features stated in claim 1.

According to the invention it has been recognized that it is notimperative in the production of a multi-component plastic product tomold the hard component first, but that it is surprisingly also possibleto start with the molding of the soft component. The injection moldingof the hard component can easily be controlled in a way so that the softcomponent is not deformed in an undesired manner by the injected hardcomponent. Because of the soft component/hard component order in theinjection molding process, new possibilities are created for thearrangement and shaping of the soft component, without putting extraeffort into designing the molded parts of the injection molding die. Thesoft component can now be injection molded at positions within the hardcomponent that would not be accessible with the reverse order, i.e. hardcomponent/soft component. The two plastic components reliably adhere toeach other via the boundary surface, resulting in a sturdy compositeplastic product in which the two plastic components can fulfill theirrespective functions. The hard component imparts strength and stiffnessto the plastic product. Additionally, the hard component can, optionallywith additional components or within the framework of an automatedassembly, constitute an assembly aid.

In a method according to claim 2, after injection molding of the softcomponent, the same fits closely against the insert component with goodadhesion, such that, for example, a gluing of the soft component can bedispensed with.

It is an additional object of the invention to provide a plastic productin which the advantages of the inventive method are applied particularlyeffectively.

This object is achieved according to the invention by a plastic productaccording to claim 3.

If the soft component is surrounded by the hard component in thecircumferential direction about a main demolding direction of theinjection molding die, it is possible because of the soft component/hardcomponent injection molding order to nevertheless produce bothcomponents by injection molding.

Materials according to claims 4 to 6, as well as 8 and 9 have provenparticularly suitable for producing an inventive plastic product havingtwo components. In lieu of a thermoplastic elastomer it is also possibleto use a silicone as the soft component. A thermoplastic elastomeraccording to claim 6 and a thermoplastic according to claim 4 adherewell to each other. Besides TPE-V and TPE-S, the following thermoplasticelastomers can be used for the soft component as well: TPE-A (amidebasis), TPE-U (urethane basis), TPE-E (ether or ester basis) and TPE-O(olefin basis). As the styrene basis, particularly SBS(styrene-butadiene-styrene block copolymers), SEBS(styrene-ethylene-butadiene-styrene copolymers) and SIS(styrene-isoprene-styrene copolymers) can be used. Because of the goodadhesion, preferred material combinations that are used are especiallypolypropylenes in the form of homo propylene, block propylene or randompropolylene as the hard component, and thermoplastic elastomers onstyrene basis, olefin basis, and cross-linked thermoplastic elastomersas the soft component. Such material combinations result in a good bondstrength and can additionally be produced economically.

A hardness range of the soft component according to claim 7 permits, inparticular, a soft component that has a good sealing function.

In a plastic product according to claim 10 the advantages of theinventive injection molding order are applied particularly effectively,since, in particular, additional adhesives can be dispensed with,thereby simplifying the production of a medically safe plastic product.

In an injection needle according to claim 11, which may be designed inthe form of a luer-type needle, for example, the soft component providesa reliable seal between an injection cannula designed in the form of aninsert component and the hard component defining the main body.

An illustrative embodiment of the invention will be explained in moredetail below, with the aid of the drawing, in which:

FIG. 1 shows a perspective view of a luer-type needle as an example fora plastic product produced according to the invention; and

FIG. 2 shows a longitudinal section through the luer-type needleaccording to FIG. 1.

A luer-type needle denoted in its entirety with 1 is an example for aplastic product produced according to the invention. The luer-typeneedle has a steel needle 2 as the injection cannula. In a left endregion 3 in FIG. 2 of the steel needle 2, which is situated opposite afree end region 4 of the steel needle 2, the steel needle 2 issurrounded over the entire circumference thereof by a soft plasticcomponent 5. The soft plastic component 5 is TPE-V, that is across-linked thermoplastic elastomer. The latter has a shore hardnessbetween A30 and A70.

The soft plastic component 5, the end region 3, and a middle region 6 ofthe steel needle 2, which in FIG. 2, adjoins the end region to theright, are surrounded over the entire circumference thereof by a hardplastic component 7. The latter forms the main plastic body of theluer-type needle 1.

The hard plastic component 7 is shaped on the outside like it isbasically known in luer-type needles, and accordingly has a standardlocking collar 8 and altogether four grasping wings 9 a that facilitatea rotating movement of the luer-type needle 1 about the longitudinalaxis of the steel needle 2 for creating a connection of the luer-typeneedle 1 to a syringe container. The locking collar 8 serves as aplastic connecting element for connecting the luer-type needle 1 to thesyringe container. The hard plastic component is made of polypropylenebut can also be produced from a different thermoplastic.

The hard plastic component 7 adheres to the soft plastic component 5 viaa boundary surface 9 that is rotation-symmetrical about the longitudinalaxis of the steel needle 2. The soft plastic component 5 serves to sealthe steel needle 2 with respect to the hard plastic component 7.

The luer-type needle 1 is produced as follows:

First the steel needle 2 is inserted as an insert into a not depictedinjection molding die. Then the soft plastic component 5 is injectionmolded in the injection molding die. The plastified soft component inthe injection molding die is injected through a tunnel gate. Afterinjecting and hardening of the soft component 5, die halves that boundthe shape of the soft plastic component 5 are separated along the maindemolding direction 10. The soft plastic component 5 is undercut-freewith respect to this main demolding direction 10.

Following the injection molding of the soft plastic component 5, thehard plastic component 7 is injection molded. The plastified hardcomponent in the injection molding die is injected through an additionaltunnel gate. The injection molding of the hard component 7 takes placeonly after the soft component 5 has hardened to a degree that anundesired deformation of the soft component 5 by the injected hardcomponent 7 is prevented. The hard component 7 is injection-moldedaround the steel needle 2 in some sections thereof and around the softplastic component 5.

After injection molding and hardening of the hard component 7 theinjection molding dies that bound the shape of the hard plasticcomponent 7 are likewise separated from each other along the maindemolding direction 10. The hard component 7 likewise is free ofundercuts along the main demolding direction 10.

The hard component 7 that is injection molded onto the soft component 5via the boundary surface 9 adhesively adheres to the soft component 5.Additionally, both the soft component 5 and the hard component 7adhesively adhere to the steel needle 2. The need for the use of anadditional adhesive is eliminated.

The soft component 5 is surrounded by the hard component 7 over theentire circumference thereof in the circumferential direction about themain demolding direction 10, which coincides with the longitudinal axisof the steel needle 2.

1-9. (canceled)
 10. A method for producing a plastic product (1), havinga hard plastic component (7) and a soft plastic component (5) thatadheres to the hard plastic component (7) via at least one boundarysurface (9), comprising the following steps: injection molding of thesoft component (5) in an injection molding die, injection molding of thehard component (7) in the injection molding die following the injectionmolding of the soft component (5), wherein prior to the injectionmolding of the soft component (5) an insert component (2) is insertedinto the injection molding die that is coated by injection molding atleast in some sections thereof with the soft component (5) and over atleast part of the circumference thereof.
 11. A plastic product (1),having a hard plastic component (7) and a soft plastic component (5)that adheres to the hard plastic component (7) via at least one boundarysurface (9) and having an insert component (2), the soft component (5)being surrounded over at least part of the circumference thereof by thehard component (7) in the circumferential direction about a maindemolding direction (10) of the injection molding die, being produced inthe injection molding die according to a method according to claim 1,wherein the insert component (2) is coated with the soft component (5)by injection molding at least in some sections thereof and over at leastpart of the circumference thereof.
 12. A plastic product (1), having ahard plastic component (7) and a soft plastic component (5) that adheresto the hard plastic component (7) via at least one boundary surface (9),the soft component (5) being surrounded over at least part of thecircumference thereof by the hard component (7) in the circumferentialdirection about a main demolding direction (10) of an injection moldingdie, being produced according to a method comprising the followingsteps: injection molding of the soft component (5) in an injectionmolding die, injection molding of the hard component (7) in theinjection die following the injection molding of the soft component (5),wherein the soft component (5) is produced of a thermoplastic elastomer(TPE), and the thermoplastic elastomer has a shore hardness in the rangeof A5 to D70.
 13. A plastic product (1) according to claim 12, whereinthe thermoplastic elastomer has a shore hardness in the range of A30 toA70.
 14. A plastic product according to claim 11, wherein the hardcomponent (7) is produced of a thermoplastic.
 15. A plastic productaccording to claim 11, wherein the hard component (7) is produced ofpolypropylene.
 16. A plastic product according to claim 11, wherein thesoft component (5) is produced of cross-linked TPE (TPE-V).
 17. Aplastic product according to claim 11, wherein the soft component (5) isproduced of a thermoplastic elastomer on styrene basis (TPE-S).
 18. Aplastic product according to claim 11, comprising its design in the formof a medical implement.
 19. A plastic product according to claim 18,comprising its design in the form of an injection needle (1) having aplastic connecting element (8) on the hard plastic component forconnecting to a syringe container.
 20. A method for producing a plasticproduct (1) and a plastic product (1) according to the invention,wherein the plastic product (1) is an injection needle.